Immediate release dosage forms of pharmaceutically active ingredient results rapid dissolution and rapid rise in plasma drug concentration within a short period of dosage form administration. Subsequently, due to metabolism and elimination, the plasma concentrations fall below the therapeutic level within period of 8-12 hours, thus requiring additional dosing, which may cause unpleasant side effects.
In order to avoid such high fluctuations in plasma concentration, the release of pharmaceutically active ingredient should be controlled in the gastrointestinal tract, so as to have a prolonged effect of drug even after a dose of once or twice a day, more preferably once a day.
Immediate release dosage forms of pharmaceutically active ingredients such as Venlafaxine hydrochloride, Bupropion hydrochloride, Pravastatin, etc results in a high plasma concentration, which causes unpleasant side effects, such as nausea or vomiting in a considerable part of the patients. In order to avoid such high plasma concentration the release of drugs should be controlled throughout the gastrointestinal tract